1. Field of the Invention
The present invention relates to an image forming apparatus, more particularly, it relates to an image forming processing.
2. Description of the Related Art
Conventionally, in an image forming apparatus provided with toner image forming units for respective colors arranged along an image bearing member for color printing, a distance and a time length from starting of image formation performed by each toner image forming unit to completion of transferring a formed toner image to a recording sheet becomes long. Therefore, in aim of shortening a printing time, a control is executed to start forming a toner image at a timing earlier than a start timing of feeding a recording sheet from a sheet feeding cassette. In an image forming apparatus where such control is executed, when a toner image arrives earlier than a recording sheet at a position where the toner image is transferred to the recording sheet, the toner image is disposed of, and then another toner image is formed and transferred to the recording sheet. Accordingly, toner particles are wasted when an arrival of a recording sheet to the toner image transferring position delays. In view of this, in an image forming apparatus disclosed in Japanese Patent Unexamined Publication No. 2004-13039, a delay in conveyance of a recording sheet is detected precociously. Then, an image formation performed by an image forming section is suspended immediately when the delay in conveyance is detected, and an arrival of the recording sheet is waited. Accordingly, disposal of an untransferred toner image is prevented from generating so that waste of toner particles is eliminated.
However, in the case of the image forming apparatus disclosed in the above-described patent document, when the recording sheets stored in the sheet cassette runs out, it would be necessary to dispose of the toner image formed before the feeding of sheets from the sheet cassette or suspend the image forming operation performed by the image forming section. Therefore, there would be a likelihood that toner particles are wasted, and it requires a long period of time to restart the image forming operation and complete the transfer of the toner image to the recording sheet.